1. Field of the Invention
The present invention relates generally to a screen placement system for an oil and gas well. More particularly, the present invention relates to a low drag flotation system for placing a screen assembly in a horizontal well.
2. Description of the Related Art
It is often desirable in the oilfield industry to drill horizontal wells to produce oil and gas. Longer horizontal sections maximize oil and gas recovery from these wells and are thus in longer lengths. These horizontal wells may either be cased holes or open holes.
It is also desirable to place screens in the horizontal wells to control the amount of sand entering the wellbore either from an open hole or perforations in a cased hole. This protects well equipment and surface equipment from sand damage. The screen assemblies, either stand-alone or gravel packed, traditionally include a screen with a washpipe inside to facilitate fluid circulation down to the bottom of the well and back up the annulus, or vice-versa. The screen assemblies are run into the well attached to a workstring, the weight of the workstring provides the necessary force to move the screen and washpipe through both the vertical and horizontal portions of the well. Once the screen is placed in the horizontal section of the well and the necessary fluid circulations are complete, the washpipe is removed from the assembly and the sand from the formation can be controlled during oil or gas production.
There is a drawback in the traditional placement of screens in a horizontal well. The weight of the workstring must be sufficient to provide a downward force that overcomes the frictional force produced by the screens rubbing against the bottom of the horizontal well bore. When the geometry conditions of the horizontal section of the well bore, such as length, tortuous and open hole caliper and others, become severe enough to create a frictional force that cannot be overcome by the workstring weight, the workstring, and thus the screen, cannot be advanced any further into the well. This may lead to damage of the screen shrouds due to the drag forces generated by the well geometry. This is obviously a limitation to the extent at which screens may be placed in a horizontal well and hinders maximum oil and gas recovery from the formation.
Thus, there is a need for an improved system and process for placing screens in a horizontal well (or an extended reach well that is subject to high drag forces).